1. Technical Field
The present invention relates to a piezoelectric device, which is, for example, acquired by mounting a temperature-sensor attached electronic component outside a package of a piezoelectric vibrator, capable of realizing high-accuracy temperature characteristics including frequency drift characteristics at the time of start-up by allowing the thermal status of the electronic component to approach that of the piezoelectric vibration device and an electronic apparatus having the piezoelectric device built therein.
2. Related Art
In the mobile communication market, the number of manufactures increases which modularize a component group for each function in consideration of mounting various electronic components, the maintenance and handling thereof, and common characteristics of components between devices. In addition, a decrease in size and cost reduction are strongly demanded in accordance with the modularization.
Particularly, the tendency of modularization becomes strong for circuit components, of which the functions and the hardware configurations are set up and which requires high stability and high capability, such as an oscillation circuit used for generating a reference frequency signal, a PLL circuit, and a synthesizer circuit. Furthermore, by packaging such a component group as a module, there is an advantage that the shield structure can be easily set up.
As examples of a surface mounting-type IC component that is built by modularizing and packaging a plurality of related components, there are a piezoelectric vibrator, a piezoelectric oscillator, a SAW device, and the like.
In JP-A-2006-191517, JP-A-2008-263564, and JP-A-2010-035078, surface mounting-type piezoelectric oscillators are disclosed which have a structure in which an IC component including an oscillation circuit and a temperature compensation circuit is assembled outside a package of a piezoelectric vibrator for achieving further miniaturization while such functions are maintained well.
In such a type of piezoelectric oscillator, a difference between the temperature of a piezoelectric vibration device disposed inside the piezoelectric vibrator and the temperature detected by the temperature sensor mounted in the IC component that is connected to the outside of the piezoelectric vibrator may easily occur. Thus, in a case where there is a temperature difference, the oscillation frequency of the oscillator is corrected based on an output of the temperature sensor that is based on incorrect temperature data. Accordingly, it is difficult to acquire stable temperature-frequency characteristics, and the frequency drift characteristics at the time of start-up deteriorate.
In order to respond to such an inconvenience, generally, a configuration has been considered in which the temperature of the insulating substrate side, to which a piezoelectric vibrating reed is directly connected, is used as a measurement point.
In JP-A-2006-191517, a technology is disclosed in which the temperature-frequency characteristics and the frequency drift characteristics are stabilized in a temperature-compensation type piezoelectric oscillator in which an IC component as an oscillation circuit device is connected to an electrode portion arranged outside a piezoelectric vibrator in which the piezoelectric vibrating reed is housed inside the package by arranging a temperature sensor near the connection terminal of the IC component connected to the electrode portion so as to decrease the difference between the temperature of the piezoelectric vibrating reed and the temperature detected by the temperature sensor.
However, the connection terminal of the IC component that is connected to the electrode portion of the piezoelectric vibrator side is configured so as to be conductive to an amplifier of the oscillation circuit. In the amplifier, since heat is generated in accordance with the operation thereof, when the temperature sensor approaches the electrode portion of the piezoelectric vibrator side within the IC component, the temperature of the heated IC component may be detected in some cases, and the above-described frequency drift characteristics may deteriorate.
Next, in JP-A-2008-263564, a technology is disclosed in which the temperature-frequency characteristics and the frequency drift characteristics are stabilized by decreasing a difference between the temperature of a piezoelectric vibration device and the temperature detected by a temperature sensor by housing a first IC component including an oscillation circuit and a temperature sensor inside a piezoelectric vibrator in which a piezoelectric vibration device is housed inside a package, connecting a second IC component including a temperature compensation circuit to the outside of the piezoelectric vibrator and arranging the temperature sensor under the same temperature environment as that of the piezoelectric vibration device.
However, a structure in which the IC component that may be originally assembled outside the piezoelectric vibrator is divided into two components, and the first IC component to which the temperature sensor is attached is housed inside the package has a low possibility of implementation in terms of cost-performance and blocks the miniaturization of the entire oscillator.
Next, in JP-A-2010-035078, a technology is disclosed in which the temperature-frequency characteristics and the frequency drift characteristics are stabilized by decreasing a difference between the temperature of a piezoelectric vibration device and the temperature detected by a temperature sensor by connecting an IC component to a concave portion arranged outside a package housing the piezoelectric vibration device in a cantilever supporting state and connecting the temperature sensor terminal of the IC component to a pillow member arranged inside the package.
However, since a conductive adhesive is interposed between the piezoelectric vibration device and a ceramic base of the package, the speed of heat transfer to the piezoelectric vibration device is slower than the speed of heat transfer to the temperature sensor terminal through the pillow member. Accordingly, it is difficult to effectively improve the frequency drift characteristics.
In any structure disclosed in the above-described technologies, the piezoelectric vibration device is configured so as to be mounted in the ceramic substrate (insulating substrate), and accordingly, it is understood that the temperature of the piezoelectric vibration device can be accurately detected by measuring the temperature of the ceramic substrate that is directly connected to the piezoelectric vibration device to which a physical distance is short. However, actually, the effect of further improving the frequency drift characteristics could not be sufficiently acquired.
As above, in a general surface mounting-type piezoelectric oscillator in which the IC component including a temperature sensor is connected to the outside of the piezoelectric vibrator, there are problems in that a difference between the temperature of the piezoelectric vibration device located inside the piezoelectric vibrator and the temperature detected by the temperature sensor arranged outside the piezoelectric vibrator may easily occur, stable temperature-frequency characteristics cannot be acquired, and the frequency drift characteristics at the time of start-up deteriorate.